1. Field of the Invention
This application generally relates to multicast initial maintenance regions for cable modems in low power mode.
2. Background Art
Cable television (CATV) systems are no longer limited to only providing television programs to viewers. In addition, CATV systems provide internet access, and/or other services to consumers via signals transmitted to customer premises by optical fibers, coaxial and other cables, such as Wi-Fi, Bluetooth®, etc., all in contrast to traditional over-the-air radio wave broadcasting of television programming.
The CATV system may utilize Data Over Cable Service Interface Specification (DOCSIS) compliant equipment and protocols to carry out a transfer of information, such as video, audio, and/or data between one or more set-top devices and one or more cable modem termination systems (CMTS). The DOCSIS Specification generally refers to a group of specifications published by CableLabs® that define industry standards for CMTS, cable modems (CMs) and control for set-top devices. In part, the DOCSIS specification sets forth requirements and objectives for various aspects of cable modem systems including, but not limited to, operations support systems, management, data interfaces, network layer, data link layer, and physical layer transport for data over cable systems. The DOCSIS interface specification entitled “Data-Over-Cable Service Interface Specifications, DOCSIS 3.0, MAC and Upper Layer Protocols Interface Specification, CM-SP-MULPIv3.0-I16-110623” is incorporated by reference herein in its entirety.
A DOCSIS cable system includes two primary components: one or more cable modems at a customer premises, and a CMTS located at a headend. As used herein, the term “downstream” refers to the transfer of information in a direction from the CMTS to the cable modems. The term “upstream” refers to the transfer of information in a direction from cable moderns to the CMTS.
A CMTS may periodically put a CM in a “sleep mode” for power saving reasons. The sleep mode is also referred to as a “low power mode.” When the CM wakes up at the end of its pre-determined periodic sleep cycle, it has to adjust its timing offset so that its upstream transmissions are aligned to the correct mini-slot boundary assigned by a CMTS. However, if the CM wakes up before the end of its sleep cycle due to an event, there is no mechanism available to quickly allow the CM to reacquire its timing by adjusting its timing offset.
The present invention will now be described with reference to the accompanying drawings. In the drawings, like reference numbers may indicate identical or functionally similar elements.